The invention relates to a portable foam fire extinguisher which generates pressurized gas stabilized fire extinguishing foam.
Fire extinguishing systems which empploy pressurized gas stabilized foam are basically known. They are designated in the art as CAFS, which stands for Compressed Air Foam System.
The first compressed air foam apparatus were built as fire extinguishing apparatus already in the 1930""s. In the same period, a portable fire extinguisher with a compressor flanged thereto for generating pressure-foam was built at one time.
Today""s CAFS fire extinguishers employ, for the generation of the compressed air needed for the foam formation, a compressor adapted to pressurize the air, which is supplied to the extinguisher medium flow at a pressure of about 7 to 10 bar. The extinguisher medium consists of water to which a foaming agent has been added. With the admission of the compressed air to the extinguisher medium flow, which is transported by a pump, additional energy is delivered to the extinguisher medium flow. This provides for a substantially increased distance for the medium discharged from the nozzle and also for a highly homogeneous foam bubble structure with an adhesion capability not known earlier. CAFS is a further development of the foam extinguishing process using water with an addition of class-A foam (wetting medium). CAFS can be used for extinguishing class A fires (solid material fires) as well as class B fires (liquid fires). With environmentally compatible foam media, low foam medium consumption (admixed to water at a rate of 0.1 to 10%); savings in extinguisher water and substantially more effective fire extinguishing capability, there is furthermore a positive environmental balance. Tests have shown that with the use of CAFS, the water consumption for extinguishing a fire can be reduced to about one sixth when compared with conventional extinguishing processes. At the same time, the safety for the firemen is increased and the stress to which they are subjected is reduced.
A CAFS system exists up to this point of the components: a fire extinguisher centrifugal pump for pumping water, an air compressor for producing compressed air and a foam admixing system for the admixing of a foaming agent and the respective controls. CAFS systems are heavy and therefore they are presently firmly installed in fire engines.
It is the object of the present invention to provide a portable fire extinguishing apparatus which can be wheeled or even be carried and which utilizes pressurized gas foam stabilization like the CAFS systems installed in fire engines and which has the same advantages but which can be used in connection with portable fire extinguishers.
Known portable fire extinguishers for liquid extinguishing media such as water or foam operate in accordance with the principle that the extinguishing medium is driven out of the extinguishing medium container by a gas (carbon dioxide, nitrogen or compressed air) from a compressed gas bottle. With appropriate pressures and nozzles, a greater foaming and water atomization can be achieved. The above-described properties of CAFS systems, however, cannot be achieved by any presently known portable fire extinguishing apparatus.
In a portable foam fire extinguisher with pressurized foam stabilization, including a container for the fire extinguishing medium, a pressurized gas bottle in communication with the container and a fire extinguisher gun connected to the container by a hose for supplying the fire extinguishing medium to the fire extinguisher gun, a mixing device is provided which is connected, by way of a pressure hose, to the pressurized gas bottle for admixing pressurized gas to the flow of the fire extinguishing medium to the fire extinguisher gun to provide in the fire extinguishing medium pressurized gas bubbles, which expand when the mixture is discharged from the gun thereby accelerating the flow from the gun while forming a foam which adheres to the surfaces covered thereby.
With the fire extinguishing apparatus with CAFS properties according to the invention, a multitude of improvements are achieved. The foam obtained with the apparatus has an atomization spectrum with smaller droplet size. The foam droplets produced thereby can therefore better enter the burning material; the foam has a greater residence time and good wetting effects which improves extinguishing capability. The fire extinguishing apparatus according to the invention is very effective for materials of the fire classes A and B.
With the apparatus according to the invention, drive gas is admitted in a dosed manner. The foam generated thereby is pressurized gas stabilized and strongly adheres to the burning materials because of its homogeneous foam bubble structure. The foam adherence to vertical or ceiling surfaces is particularly improved so that the foam adheres to these surfaces for some time and can therefore be used much more effectively than water. Tests have shown that the pressure gas stabilized foam as produced by the apparatus according to the invention adheres even to glass panels for an extended period of time.
An embodiment of the invention will be described below in greater detail on the basis of the accompanying drawings.